JP4350012B2 - Packet radio communication system - Google Patents

Description

  The present invention relates to a packet transfer wireless communication system, and more particularly to an adaptive modulation wireless packet communication system.

  In recent years, a digital transmission system such as a multi-level QAM system has been used as a wireless communication system in which user information and control information are transferred in packets. At this time, modulation is performed according to the condition of the transmission path. There is a case where a so-called adaptive modulation wireless communication system that changes the system is used (see, for example, Patent Document 1 and Patent Document 2).

  Here, in the case of a transmission path with good transmission characteristics, this adaptive modulation system selects a modulation system with a large number of multi-values capable of high-speed transmission, such as a 64QAM system, and the condition of the transmission path is very good. When there is not, for example, switching is made sequentially to a low-speed modulation system having a low multi-value number, such as a 16QAM system, a QPSK modulation system, or a BPSK modulation system.

  An example of the prior art of a packet radio communication system using such an adaptive modulation scheme will be described. In this case, the system includes two radios 10 and 20 that perform packet communication with each other as shown in FIG. And these are connected via a wireless transmission system.

  Each of the radio devices 10 and 20 includes modulation units 110 and 210, adaptive modulation control units 120 and 220, demodulation units 130 and 230, and radio control units 140 and 240, and further includes radio control units 140 and 240. Are connected to Ethernet (registered trademark) 15 and 25, and are connected to a LAN (not shown).

  Here, when one of the wireless device 10 and the wireless device 20 is on the transmitting side, the other is on the receiving side, and if necessary, the transmitting device becomes the transmitting side or the receiving side, A packet including user information and control information is transferred from one to the other.

  Accordingly, it is assumed that the wireless device 10 is on the transmitting side and the wireless device 20 is on the receiving side. Then, during communication, radio apparatus 20 on the receiving side uses part of the demodulated data by demodulating section 230, estimates the state of the transmission path (propagation path) by adaptive modulation control section 220, and performs adaptive modulation control. Unit 220 stores the estimated propagation path condition as band information.

  As a method for estimating the propagation path condition at this time, there are, for example, a method using the received electric field strength, a method using the error output of the equalizer, and a method using an estimated bit error rate by re-encoding after error correction.

  After that, when the wireless device 20 becomes the transmitting side and the wireless device 10 becomes the receiving side, the adaptive modulation control unit 220 of the wireless device 20 that becomes the transmitting side then stores the stored band information. Is input to the modulation unit 210 and the radio control unit 240, whereby the modulation unit 210 selects an optimum modulation method from among a plurality of modulation methods prepared in advance according to the band information, and switches to it to switch the data. The wireless control unit 240 switches the data processing method for packet transfer, that is, the packet data transfer processing method according to the modulation method selected at this time, according to the band information.

  On the other hand, at this time, the radio device 10 which has become the receiving side can determine which modulation method is used to transmit the currently transmitted data based on the information included in the received data. Accordingly, the demodulation operation by the demodulator 130 can be switched in accordance with the current modulation method, and the received packet can be transferred.

  Next, the radio control units 140 and 240 will be described in detail. As shown in FIG. 5, these units include an interface unit 400 composed only of hardware and a CPU equipped with a predetermined OS, and necessary software processing is performed. It is composed of two types of blocks of the control unit 410 that can be performed.

  With these blocks, data is input from the Ethernet (registered trademark) 15 and 25, processing necessary for packet transfer is executed, and data is output to the modulators 110 and 120.

  At this time, if all of the transfer of data input from the Ethernet (registered trademark) 15 and 25 is to be processed by the CPU of the control unit 410, the load becomes heavy and a high-speed CPU or a plurality of CPUs are required.

  Therefore, as shown in FIG. 5, the processing by the hardware of the interface unit 400 and the processing by the software of the control unit 410 are used in combination, and these can be switched and used so that cost reduction and power consumption can be obtained. I have to. At this time, regarding the hardware of the interface unit 400, only the buffer is illustrated in an aggregated manner.

  Here, it is assumed that, for example, four systems of 64QAM, 16QAM, QPSK, and BPSK are prepared as modulation systems for the adaptive modulation system, and at this time, 64QAM that provides the highest speed transmission is selected.

  Then, at this time, the switch SW10 of the interface unit 400 is set to the OFF side, the data processing is performed by the hardware of the interface unit 400, and the processing necessary for packet transfer, that is, the packet data transfer processing method is left to the hardware. The CPU of the control unit 410 is not required to operate at high speed. The operation of the switch SW20 will be described later.

  On the other hand, if the modulation method is switched from 64QAM to a low-value modulation method, for example, BPSK, QPSK, or 16QAM, by the band information from the adaptive modulation control units 120 and 220, and the wireless transmission speed is reduced, This time, the switch SW10 is turned on to send data to the control unit 410, and the processing necessary for packet transfer, that is, the packet data transfer processing method is left to the CPU software, and the data is transferred to the modulation units 110 and 120. To do so.

  Next, the switching operation of the switch SW10 in the control unit 410 and the modulation method switching by the modulation units 110 and 120 will be described in detail with reference to FIG.

  First, in the case where the modulation units 110 and 120 are switched from a modulation method such as BPSK, QPSK, or 16QAM having a low multi-value number to a modulation method such as 64QAM having a high multi-value value, based on band information from the adaptive modulation control units 120 and 220. That is, when the wireless transmission speed is switched from low speed to high speed, the ON / OFF switching operation of the switch SW10 and the switching operation of the modulation schemes of the modulation units 110 and 120 are performed at the same timing as shown in FIG. It is like that.

  Similarly, the timing for switching from a modulation scheme such as 64QAM having a high multilevel to a modulation scheme such as BPSK, QPSK, or 16QAM having a low multilevel is performed at the same timing as shown in FIG. It has become.

  Next, returning to FIG. 5, the operation of the switch SW20 will be described. When there is data only in either the buffer of the interface unit 400 or the buffer of the control unit 410, the switch SW20 starts from the buffer with the data. It works to switch to transfer data.

  Normally, at the time of switching of the switch SW10, the data of the path before switching remains in the buffer, and therefore both the data of the path before switching and the data after switching exist in the buffer even after switching.

Therefore, the switch SW20 is alternately switched, and after the data buffer before switching is emptied, switching to the data buffer after switching is performed so that no data transfer remains.
JP 2004-112780 A JP 2004-128888 A

  The above prior art does not give consideration to the proper processing of data in switching the modulation method, and has the following problems.

  In the packet transfer path switching operation by the adaptive modulation system, the modulation system that can secure a sufficient transmission rate such as 64QAM is switched from a modulation system that can secure a sufficient transmission rate such as BPSK, QPSK, and 16QAM. The transmission rate drops here.

  At this time, in the above prior art, the switching operation of the switch SW10 of the radio control units 140 and 240 and the modulation scheme of the modulation units 110 and 210 are made at the same timing. The modulation method is switched before all the data transferred by the modulation method having a high number of values is discharged.

  For this reason, as shown in FIG. 6B, while the data transmitted by 64QAM remains, the modulation system changes to a lower modulation system such as 16QAM, and this remains. Since the data must be transferred from the buffer at a low transmission rate, there is a problem that the data transfer efficiency is lowered.

  Further, as in this prior art, when the switching operation of the switch SW10 of the radio control units 140 and 240 and the modulation scheme of the modulation units 110 and 210 is made at the same timing based on the band information calculated by the adaptive modulation control units 120 and 220 There is a possibility that data that performs data transfer by hardware processing via the interface unit 400 and data that performs data transfer by software processing via the control unit 410 may be mixed in the radio control units 140 and 240. In this case, there is a possibility that the order of data sent to the modulators 110 and 210 and the demodulator units 130 and 230 may be changed by alternately switching the switch SW20. Further, data is stored in the buffer of the controller 410. Overflow and packet loss may occur. In this case, the capacity is increased to prevent data overflow. Necessary to provide a buffer occurs.

  The present invention has been made in view of the above-described problems of the prior art, and its purpose is to prevent the possibility of data misordering, buffer overflow, packet loss, and the like, and to reduce packet data transfer efficiency. An object of the present invention is to provide a packet radio communication system of an adaptive modulation system that is not likely to be accompanied.

  An object of the present invention is to provide a packet radio communication system that switches a packet data transfer processing method in response to switching of a modulation method by an adaptive modulation method. When switching to the packet data transfer processing method, a delay time is given to the switching timing of the modulation method.

  At this time, when the variable control modulation method is switched, the delay time is changed according to the data transfer rate according to the modulation method before the switching, and the delay time is controlled to be shorter as the data transfer rate is higher. Even so, the above object can be achieved.

  According to the present invention, in the packet radio communication system of the adaptive modulation scheme, the switching timing of the packet data transfer process and the switching timing of the modulation scheme are shifted, so that there is a possibility that the packet data transfer efficiency may be reduced during the switching operation of the modulation scheme. And efficient packet transfer can be performed.

  As a result, according to the present invention, there is no possibility that the data is out of order, the buffer overflows, or the packet loss occurs, so that the packet transfer can be performed at low cost and with high reliability.

  Hereinafter, a packet radio communication system according to the present invention will be described in detail with reference to embodiments shown in the drawings.

  FIG. 2 shows an embodiment of a packet radio communication system according to the present invention, in which a radio device 1 and a radio device 2 on the transmission side and the reception side face each other and are connected via a radio transmission path. Each of the wireless devices 1 and 2 includes modulation units 11 and 21, adaptive modulation control units 12 and 22, demodulation units 13 and 23, and radio control units 14 and 24. The outputs of the radio control units 14 and 24 are Ethernet. (Registered Trademarks) 15 and 25 are connected to a LAN (not shown).

  At this time, the wireless devices 1 and 2 in this embodiment correspond to the wireless devices 10 and 20 in the prior art of FIG. Corresponds to the adaptive modulation control units 120 and 220, the demodulation units 13 and 23 correspond to the demodulation units 130 and 230, and the radio control units 14 and 24 correspond to the radio control units 140 and 240, respectively.

  Therefore, in this embodiment as well, the configuration of the entire system viewed as a block is the same as that of the packet radio communication system according to the prior art described in FIG. 4, but in the embodiment of FIG. Is different in that QoS (Quality of Service) control is applied to the data. This QoS control will be described later.

  However, except for this point, the packet transfer processing is roughly the same as the conventional technology, so the following description will focus on the differences from the conventional technology, and the same operations as the conventional technology will be described briefly. .

  In FIG. 2, in this embodiment as well, as in the case of the prior art, the wireless device 1 and the wireless device 2 become a transmitting side and a receiving side as needed, and packets including user information and control information are transferred. It is like that.

  When the wireless device 1 is the transmitting side and the wireless device 2 is the receiving side, the wireless device 2 which is the receiving side receives the received field strength, the error output of the equalizer, and the estimated bit error due to re-encoding after error correction. The state of the transmission path (propagation path) is estimated by the adaptive modulation control unit 22 based on the rate and stored as band information.

  When the wireless device 2 becomes the transmitting side and the wireless device 1 becomes the receiving side, the transmitting-side wireless device 2 selects the optimum modulation method based on the band information, and the data is transmitted from the modulation unit 21 switched to that. In the wireless control unit 24, the data processing method for packet transfer, that is, the packet data transfer processing method is switched according to the modulation method selected at this time by the band information.

  In addition, in the radio device 1 on the receiving side, the modulation scheme is determined based on the information included in the received data, the demodulation operation by the demodulator 23 is switched in accordance with the current modulation scheme, and the received packet is transferred. Done.

  Next, the radio control units 14 and 24 in the embodiment of FIG. 2 will be described with reference to FIG. 3. As with the prior art (FIG. 5), these may not use a high-speed CPU or a plurality of CPUs. It has two types of blocks: an interface unit 40 consisting only of hardware and a control unit 41 having a CPU that can perform necessary software processing by installing a predetermined OS, thereby reducing cost and power consumption. Can be obtained.

  Also in FIG. 3, the hardware of the interface unit 40 is aggregated and only the buffer is shown, and data is input to the two types of blocks from the Ethernet (registered trademark) 15 and 25, and is necessary for packet transfer. It is designed to execute various processes.

  At this time, the control unit 41 in this embodiment performs the above-described QoS control in the data transfer process by the software of the CPU, thereby further improving the reliability. For example, a routing process may be performed as a data transfer process by another software.

  Here, in this embodiment as well, it is assumed that four systems of 64QAM, 16QAM, QPSK, and BPSK are prepared as the modulation system for the adaptive modulation system, and 64QAM that is the fastest transmission is selected.

  Then, at this time, the switch SW1 of the interface unit 40 is set to the OFF side, and processing necessary for packet transfer is left to the hardware so that the CPU of the control unit 41 does not require high-speed operation. Is the same as the prior art.

  Here, the switching control of the switch SW1 at this time is executed by a control CPU provided in the wireless control units 14 and 24, although not shown. This also applies to the switch SW2 described later. Further, in the prior art described with reference to FIGS. 4 and 5, the switches SW10 and SW20 are the same and are provided in the radio control units 140 and 240. It is executed by the control CPU.

  Next, the band information from the adaptive modulation control units 12 and 22 is switched from 64QAM to a modulation method having a low multi-level number, for example, BPSK, QPSK, or 16QAM, and the wireless transmission rate is lowered. As in the prior art, this time the switch SW1 is turned on, thereby sending data to the control unit 41 and leaving the processing necessary for packet transfer to the CPU software.

  Next, the switching operation of the switch SW1 of the control unit 41 and the switching of the modulation method by the modulation units 11 and 12 in this embodiment will be described in detail with reference to FIG.

  First, according to band information from the adaptive modulation control units 12 and 22, the modulation units 11 and 12 are switched from a modulation method such as BPSK, QPSK, or 16QAM having a low multi-value number to a modulation method such as 64QAM having a high multi-value value. That is, when the wireless transmission speed is switched from low speed to high speed, the ON / OFF switching operation of the switch SW1 and the switching operation of the modulation method of the modulation units 11 and 12 are performed at the same timing as shown in FIG. It is like that.

  Therefore, in this case, that is, when the wireless transmission speed is switched from low speed to high speed, this embodiment is also the same as the prior art described with reference to FIG. 6 (a). In the case of switching from a high modulation scheme such as 64QAM to a modulation scheme such as BPSK, QPSK, or 16QAM having a low multi-value number, that is, the timing when the wireless transmission speed is switched from high speed to low speed, it has been described with reference to FIG. It is different from the prior art.

  This is one of the features of this embodiment. Accordingly, hereinafter, the case where the wireless transmission speed is switched from high speed to low speed in this embodiment will be described with reference to FIG.

  First, in the interface unit 40 of this embodiment, the ON / OFF switching operation timing of the switch SW1 is the switching timing 1, and the switching operation timing of the modulation schemes of the modulation units 11 and 12 is the switching timing 2.

Then, a time difference is provided between the switching timing 1 and the switching timing 2 so that a delay of a predetermined time is given to the switching timing 2 with respect to the switching timing 1. That is, assuming that the delay time at this time is Δt, the switching timing 1 is time t ₀ , and the switching timing 2 is time t ₁ , the relationship is t ₁ = t ₀ + Δt.

  Then, in this embodiment, as shown in FIG. 1B, after the switch SW1 is switched from OFF to ON at the switching timing 1, the modulation of the modulation units 11 and 12 is performed at the switching timing 2 after the lapse of time Δt. The system is switched from a modulation system having a high multi-level number (here, 64QAM) to a modulation system having a low multi-level number (here, 16QAM).

  Here, assuming that the delay time Δt is 1 second (sec), in this case, after the switch SW1 is switched from OFF to ON, the modulation system of the modulation units 11 and 12 is switched after 1 second has elapsed. As a result, even after the switch SW1 is switched from OFF to ON, the modulation schemes of the modulation units 11 and 12 remain high modulation schemes (here, 64QAM) for one second.

  Therefore, the data processed by the hardware of the interface unit 40 is modulated by the modulation units 11 and 12 operating in the high-level modulation scheme even after the switch SW1 is switched from OFF to ON. The transfer process is continued for 1 second. During this period, the transfer process is performed at a high wireless transmission speed, so the transfer process is performed in a short time.

  Then, after all the data processed by the hardware of the interface unit 40 is transferred, the modulation method of the modulation units 11 and 12 is switched to a modulation method having a low multi-level number at the switching timing 2, where adaptive modulation is performed. The modulation method switching by the method is completed.

  Therefore, according to this embodiment, since the data transfer process is completed in a short time even when the wireless transmission speed is switched from high speed to low speed by the adaptive modulation method, it is possible to suppress a decrease in data transfer efficiency.

  In addition, since the data transfer process is completed in such a short time, there is less possibility that data will be mixed in the radio control units 14 and 24. Therefore, according to this embodiment, the modulation unit 11, 21 and the order of data sent to the demodulation units 13 and 23 are less likely to be misplaced, so that the reliability can be improved. Further, data overflows in the buffer of the control unit 410 and packet loss is reduced. Since the possibility of the occurrence is reduced, it is not necessary to increase the capacity of the buffer, and the cost can be suppressed.

  By the way, in the above embodiment, the delay time Δt at the switching timing 1 and the switching timing 2 is set to a fixed time (1 second). When the modulation method is switched to a lower modulation method, it is determined by the data transfer rate according to the modulation method having a high multilevel number, and the shorter the data transfer rate, the shorter the modulation method.

  Therefore, the delay time Δt is not set as a fixed time, but may be increased or decreased according to the modulation method before switching, and as described above, the delay may be variably controlled so as to be shorter as the data transfer rate is higher. The data transfer efficiency can be further improved.

  Therefore, according to the embodiment described above, in the packet transfer wireless communication system, only by shifting the data transfer process and the switching timing of the modulation method, the modulation method is changed to the multi-value modulation method by the modulation method switching operation of the adaptive modulation method. When switching from a low modulation method to a high-value modulation method, the data transfer is switched from software processing via the control unit to hardware processing via the interface unit, or when the modulation method is high-value modulation. When the data transfer is switched from hardware processing via the interface unit to software processing via the control unit when switching from a modulation method to a low-value modulation method, the modulation unit By shifting the timing of switching the modulation method in the wireless controller, the wireless controller Data transfer efficiency can be achieved by performing all transfer processing without leaving the data at the time when data was transferred in the mode, and operating the wireless control unit corresponding to the low-speed modulation method with a low multi-valued number. Can provide a good system.

It is explanatory drawing of the switching timing by one Embodiment of the radio | wireless communications system by this invention. 1 is a block diagram showing an embodiment of a packet radio communication system according to the present invention. It is a block diagram which shows the detail of the radio | wireless control part in one Embodiment of this invention. It is a block diagram which shows an example of the packet radio | wireless communications system by a prior art. It is a detailed block diagram of the control part in an example of the packet radio | wireless communications system by a prior art. It is explanatory drawing of the switch timing by an example of the radio | wireless communications system by a prior art.

Explanation of symbols

1, 2: Radio equipment (radio equipment in one embodiment of the present invention)
11, 21: Modulation unit 12, 22: Adaptive modulation control unit 13, 23: Demodulation unit 14, 24: Radio control unit 15, 25: Ethernet (registered trademark)

Claims (2)

In a packet radio communication system of a method for switching a packet data transfer processing method in response to switching of a modulation method by an adaptive modulation method,
When switching the modulation scheme from a modulation scheme having a high multi-level number to a modulation scheme having a low multi-level number, a delay time is given to the switching timing of the packet data transfer processing scheme from the switching timing of the modulation scheme. A packet radio communication system. The packet radio communication system according to claim 1,
The delay time is variable controlled when the modulation method is switched, and is changed according to the data transfer rate by the modulation method before the switching, and is controlled to be shorter as the data transfer rate is higher. Packet radio communication system.

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